This invention relates to a liquid film type, anion-selective electrode, and particularly to a liquid film type, anion-selective electrode based on a polymer support film suitable for measuring inorganic anions such as a chloride ion.
Liquid film type, anion-selective electrodes are less susceptible to influences by halogen, sulfides, etc., than inorganic solid film type electrodes and have been used for measuring body liquids such as blood, urine, etc. Known typical liquid film type electrodes are anion-selective electrodes comprising a sensitive film which is based on ion exchange liquid film and which supports a quaternary ammonium salt as a sensitive substance in a synthesized polymer support of polyvinyl chloride, etc. as disclosed, for example, in U.S. Pat. No. 4,349,426.
These liquid film type electrodes have problems, when chloride ions in body fluids are to be measured, such as a large error of measurement due to influences by substances deposited on the surface of the sensitive film and a difficulty to obtain a high responsiveness. Thus, many attempts have been so far made to solve these problems. For example, Japanese Patent Application Kokai (Laid-open) No. 54-89689 proposes to use methyltridodecylammonium chloride as a sensitive substance and o-nitrophenyloctylether as a plasticizer to improve the response speed, and Japanese Patent Application Kokai (Laid-open) No. 57-77952 proposes to use methyltridodecylammonium chloride as a sensitive substance and n-tetradecyl alcohol as a plasticizer to reduce adsorption of protein, etc.
However, these proposed attempts still suffer from such problems that errors of measurement are considerably increased by improving the responsiveness, whereas the responsiveness is considerably deteriorated by improving a composition to reduce the errors of measurement. Thus, development of practically distinguished anion-selective electrodes has been keenly desired.